The present invention relates generally to geared pumps and motors and, in particular, to a variable capacity geared apparatus usable as either a pump or a motor.
Numerous types of variable volume gear pumps and motors are found in the prior art. For example, the U.S. Pat. No. 2,293,126 shows a gear pump or motor having a gear housing movable by a lever secured to a stub shaft.
The U.S. Pat. No. 2,754,765 shows a variable displacement pump that includes a drive gear and a follower gear that displaces radially when a fluid pressure on an accumulator exceeds a predetermined value.
The U.S. Pat. No. 3,110,265 shows a gear type fluid handling device that includes an upper gear movable with respect to a lower gear via a lever.
The U.S. Pat. No. 3,588,295 shows a variable output gear pump or motor apparatus that includes an output gear assembly movable relative to an input gear assembly via a control output assembly that diverts fluid to the input side of the pump.
The U.S. Pat. No. 4,740,142 shows a variable capacity gear pump with pressure balance for transverse forces that includes a fixed gear and a gear axially movable relative to the fixed gear alternatively via a spring, via hydraulic pressure through bores, and via a controller.
The U.S. Pat. No. 5,184,947 shows a fully variable output hydraulic gear pump having an axially translatable gear and a fixed gear. The translatable gear is movable through a gear sleeve via hydraulic pressure controlled by a hydraulic cylinder or a motorized screw.
The U.S. Pat. No. 5,306,127 shows a fluid pump with axially adjustable gears having telescoping first and second cylindrical housings and mounted in the pump housing.
The U.S. Pat. No. 5,620,315 shows a gear pump for feeding of fluids that includes a fixed gear and a gear that is axially movable between a pair of shiftable walls.
The U.S. Pat. No. 5,724,812 shows a variable displacement apparatus that includes housing parts that are interconnected for relative axial movement.
The U.S. Pat. No. 6,283,735 shows a variable-delivery external gear pump that includes a steel compression spring that moves one of the gears axially with respect to the other gear based on pressure in the pump casing.
The U.S. Patent Application No. 2001/0024618 shows an adjustable displacement gear pump having a follower assembly that is operable to move an idler gear within a pump housing relative to a pump gear in order to vary the output of the pump. The pump gear includes a gear complement and the idler gear includes a gear complement for providing a seal for the gears. The displacement of the pump is varied by moving the follower assembly from a proximal end to a distal end of the pump. The follower assembly moves both the pump gear and the idler gear to vary a pump chamber length.
The U.S. Pat. No. 2,484,789 shows a variable displacement pump and motor that includes an outer gear and an inner gear mounted on a shaft and disposed between a pair of bulkheads. Displacement of the pump/motor is varied by moving the bulkhead axially along a shaft. Fluid is introduced to the gears via radial ports formed in the outer gear.
The U.S. Pat. No. 3,805,526 shows an embodiment of a variable displacement rotary hydraulic machine having a gerotor assembly that includes an inner element, an outer element, a plug that rotates with the inner element, and a plug that rotates with the outer element. The capacity and/or displacement of the pump or motor are varied by mechanical movement of a locating ring. Fluid is supplied to the elements through ducts.
The U.S. Pat. No. 4,492,539 shows a variable displacement gerotor pump having a housing that achieves variable displacement by positioning an axis of an outer rotor eccentric to the axis of an inner rotor by movement of a variator in the housing. The movement of the variator is alternately manual or hydraulic.
The U.S. Pat. No. 4,493,622 shows a variable displacement motor that includes an outer gerotor gear and an inner gerotor gear that transmits torque to an output shaft via a wobble shaft. The displacement of the motor is varied by varying the eccentricity between the meshing gears of the gerotor gears. A second embodiment of the motor includes a pair of gerotor gear sets.
The U.S. Pat. No. 4,812,111 shows a variable displacement apparatus usable as a pump or motor that includes an inner rotor movable relative to an outer rotor for varying the displacement of the apparatus. A distributor plate guides and directs flow from inlet and outlet ports through integral chambers and to the pump or motor displacement chambers. The distributor plate is fixed axially with respect to the inner rotor.
The U.S. Pat. No. 6,244,839 shows a pressure compensated variable displacement internal gear pump that includes an inner gerotor, a port plug, and an outer gerotor axially aligned on a drive shaft. The inner gerotor and the port plug slide inside the outer gerotor and vary displacement of the pump by opening and closing various intake and discharge ports defined by the outer gerotor.
The U.S. Pat. No. 6,758,656 shows a multi-stage internal gear/turbine fuel pump that includes a gear pumping module having an internal gear and an external gear and a turbine pumping module attached on a shaft.
The U.S. Pat. No. RE 31,067, and the U.S. Pat. Nos. 4,426,199, 4,545,748, 4,563,136, and 4,824,347 show gerotor or internal gear pumps or motors.
It remains desirable, therefore, to provide an efficient variable capacity internal or external gear pump.